A metal-air battery has a high energy density, and thus has attracted attention as a next-generation battery. The metal-air battery generates electricity in a state where a metallic electrode containing an electrode active material as a fuel is set as an anode, and an air electrode is set as a cathode.
Examples of a representative metal-air battery include a zinc-air battery in which metal zinc is set as an electrode active material. In the zinc-air battery, it is considered that an electrode reaction similar to the following Chemical Formula 1 progresses in the cathode.O2+2H2O+4e−→4OH−  (Chemical Formula 1):
In addition, it is considered that an electrode reaction similar to the following Chemical Formulae 2 and 3 progresses in the anode.Zn+4OH−→Zn(OH)42−+2e−  (Chemical Formula 2):Zn(OH)42−→ZnO+2OH−+H2O  (Chemical Formula 3):
In addition, it is considered that metal zinc (Zn) that is the electrode active material is dissolved once in an electrolytic solution in the form of Zn(OH)42− along with the progress of the electrode reaction, and when concentration of the ion reaches saturation, the metal zinc settles in the form of ZnO in the electrolytic solution.
When power generation by the metal-air battery continues, the electrode active material contained in the metallic electrode is consumed, and thus it is necessary to supply a new electrode active material to the metal-air battery. As a method of supplying the electrode active material, a method of inserting an anode assembly, in which a plurality of metallic electrodes are connected to each other on a support, into a metal-air battery main body, a method of inserting the metallic electrode into a bag-shaped structure that is provided at the inside of the metal-air battery, a method of inserting a fuel battery into a case-shaped metal-air battery main body, and the like are known (For example, refer to PTL 1, PTL 2, and PTL 3).